Compound heterozygous genotype is associated with protracted juvenile neuronal ceroid lipofuscinosis

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Abstract
We present a clinicopathological study and the first molecular genetic analysis of a family with 2 siblings affected by a rare, protracted form of juvenile neuronal ceroid lipofuscinosis (JNCL). Molecular genetic studies showed that both siblings, in addition to being heterozygous for the 1.02‐kb CLN3 deletion, a common mutation in JNCL, also had a G‐to‐A missense mutation at nucleotide 1,020 of the CLN3 cDNA sequence on the non‐1.02‐kb deletion chromosomes. This point mutation resulted in a substitution of glutamic acid by lysine at position 295 of the CLN3 protien. Thus, a single point mutation at residue 295 of the CLN3 protien in protracted JNCL may underlie the phenotype in this form, which differs from that in classic JNCL.